The analysis of tissue samples removed at surgery or autopsy can reveal important clues in our understanding of various pathological states. For example, the analysis of the DNA obtained from tumor biopsy can provide valuable insight into the genetic defects that underlie malignant transformation. Freshly obtained samples must immediately be stored in a tissue fixative in order to prevent decomposition. The ideal fixative should (i) permit recovery of high molecular weight nucleic acids (DNA and RNA) from the sample for molecular analysis and (ii) preserve the morphology and lmmunogenicity of specimens allowing routine anatomical pathology investigation.
A commonly used fixative is 10% buffered neutral formalin (BNF). Samples stored in BNF are adequate for pathology analysis. However BNF degrades nucleic acids and therefore samples are not useful for the extraction of high molecular weight DNA or RNA. Solutions of 95% ethanol have been shown to be effective in preserving DNA in a limited number of cases. However, samples stored in 95% ethanol are not satisfactory for the pathologist. Consequently, when one wants to obtain samples for both DNA extraction and pathology it is necessary to take the fresh biopsy sample and store part of it in BNF and another part in, for example, liquid nitrogen. This conventional method requires that a technician is on call during surgery in order to properly store the sample.
Therefore, in view of the foregoing it is desirable to develop a tissue fixative that permits the recovery, weeks or even months after fixation, of high molecular weight nucleic acids for molecular genetic analysis, while at the same time preserving the morphology of the sample for analysis by the pathologist.